Different past tense for various *et words [duplicate]
There is a set of English irregular verbs that have four unusual characteristics:
- they consist of only one syllable
- they end in a dental stop, /d/ or /t/
- they have a lax or low vowel - /ɛ ɪ æ ɔ ʊ ə ɚ/
- they are not inflected for past tense or past participle
Examples are the verbs bet, let, set, as noted, but also others, like cut, spit, and cast.
There are around 25 verbs in the list:
- beat,
bet,
bid,
burst,
cast,
cost,
cut,
fit,
hit,
hurt,
knit,
let,
put,
quit,
rid, set, shed, shut, slit, spit, split, spread, thrust, upset, wed.
As can be seen, the verbs jet, net, pet, wet, and vet are not in the list,
so those are regular verbs with regular past tense forms in -ed.
Why those verbs and not others? Because that's the way irregularities work.
Irregular verbs do not happen by rule -- irregular means 'not by rule'.
Many of the words with irregular past forms are very old (derived from Old or Middle English), while most of those with regular forms have been introduced more recently. For example, "vet" is fairly new, originating from the late 19th century and surprisingly seems to be related to "veterinarian".
Irregular
let: from Old English lǣtan (Wiktionary)
bet: from 16th-century criminal slang, likely from abet or Old English bætan (Wiktionary)
set: from Old English settan (Wiktionary)
hit: from late Old English hyttan, hittan
Regular
vet: late 1800s
jet (as a verb): 1690s, from French jeter "to throw, thrust"
net (as a verb): 1400s
pet: Sense of "to stroke" is first found 1818
wet: from Old English wætan (*This may be an exception, but as noted in a comment, the irregular past form "wet" is used in some senses.)