How did we get ‘deft’ and ‘daffy’ from “daft”?

[ Etymonline for 'daft (adj.)'] Old English gedæfte "gentle, becoming," ... from PIE * dhabh- "to fit together" (see fabric). Sense of "mild, well-mannered" (c. 1200).

[ Etymonline for 'daffy'] 1884, perhaps from daft (adj.), or from obsolete daffe "a halfwit"

The Oxford University Press website makes the following observations

[Blog.oup.com:] Daft goes back to Old English, in which its sense was “mild, gentle, meek” (the root, again on the evidence of Gothic, meant “be, become fit”). Why “fit, suitable” yielded “stupid” and “bereft of sound judgment” is far from clear; nor does the presence of Middle Engl. daff “simpleton, fool” of unknown origin dispel the obscurity. To confuse us even more, we notice that daft is a doublet of deft. Originally, deft also meant “gentle, meek,” later “skillful; neat; pretty.” The starting point of daft and deft was the same, namely “fitting, convenient.” ...

Daft and deft are antonyms, but I always mistake one for the other.

• How can I avoid mixing the two up?

I also included ‘daffy’ because I'm unsure if the OUP blog's citation of 'Middle English daff' refers to ‘daffy’. Does it?

Solution 1:

Metaphorical extension does amazing things to cause a root meaning to radiate out in various directions, quoting the linguist Jeffrey Henning:

Radiation is metaphorical extension on a grander scale, with new meanings radiating from a central semantic core to embrace many related ideas.

• The word head originally referred to that part of the human body above the rest.

• Since the top of a nail, pin or screw is, like the human head, the top of a slim outline, that sense has become included in the meaning of head.

• Since the bulb of a cabbage or lettuce is round like the human head, that sense has become included in the meaning of head.

• Know where I'm headed with this?

• The meaning of the word head has radiated out to include the head of a coin (the side picturing the human head), the head of the list (the top item in the list), the head of a table, the head of the family, a head of cattle, $50 a head

Wikipedia emphasis mine and reformatted for clarity

Semantic deterioration also shifts words from their root meaning:

A disapprovement in the meaning of a word.

• The term knave meant originally (Old English) ‘male servant’ from ‘boy’ (cf. German Knabe) but deteriorated to the meaning of ‘base or coarse person’, having more or less died out and been replaced by boy.
• Villain developed from ‘inhabitant of a village’ to ‘scoundrel’.
• The word peasant is used now for someone who shows bad behaviour as the word farmer has become the normal term. In official contexts, however, the term ‘peasant’ is found for small and/or poor farmers.

Types of Semantic Change, University of Duisburg-Essen, Reformatted for clarity.

Semantic amelioration shifts words in the opposite direction:

An improvement in the meaning of a word.

• The term nice derives from Latin nescius ‘ignorant’ and came at the time of its borrowing from Old French to mean ‘silly, simple’ then ‘foolish, stupid’, later developing a more positive meaning as ‘pleasing, agreeable’.

Types of Semantic Change, University of Duisburg-Essen, Reformatted for clarity.

In this case, these three forces seem to radiate the meaning of two words from the root in opposing directions:

The etymological theory, which is plausible though not 100% certain, suggests that the PIE dhabh- "to fit together" developed slowly toward its present deft- "skillful" by a metaphorical extension of the gentle skills used to fit together fabric, a word that shares the same PIE root dhabh-. That metaphorical extension is intuitively understood in the picture of a deft boy:

Photo © Jena P. Jones/f2photos.com

Apparently, deft and daft shared a sense of "gentle, and becoming" in Old English. Their different pronunciations (which only later formalized into spellings) experienced different metaphorical extension in Middle English. Deft continued to develop the meaning of "skillful".

But daft seems to have experienced systematic semantic deterioration from "mild-mannered" (1200), to "dull and awkward" (1300), and eventually to "foolish and crazy" (1500) under the added influence of the third word daffy. In the same way that the weaker children at school become awkward in the presence of the stronger children, we can imagine some mild-mannered people being oppressed by skillful manipulators, who label themselves deft, and their victims daft. Continuing this pattern of derogatory differentiation over generations would reinforce the semantic deterioration of daft:

jackfrost.blog.co.uk

It is not certain, but it seems reasonable that daffy developed from daft. The adjective suffix -y indicates "full of or characterized by," and eventually the sense of diminutive pet suffix -y may have added to the semantic deterioration of daffy. Even if the direct source of daffy was not daft, but rather daffe - "a halfwit", the phonetic analogy of daft and daffy could have easily added to the semantic deterioration of daft.

This metaphorical extension, semantic deterioration and analogy took place over time, only becoming obvious to us by comparative linguistics. The way people used the words deft and daft slowly changed, until their meanings became opposite, and the way people used daffy reinforced the distinction.

Recommended Reading: Analogy and Morphological Change, by David Fertig