Origin, meaning, and historical change (if any) of the idiom 'stem the tide'

Solution 1:

According to Etymonline, the original meaning of stem is to stop, to hold back:

Stem the tide:

• Phrase to stem the tide is literally "to hold back the tide," but often is confused with stem (v.2) "make headway against."

Also from the OED:

• (trans.) To stop, check; to dam up (a stream, or the like). When used fig. in phrases like ‘to stem the tide’, this verb is sometimes confused with stem v.4, "to make headway against".

  • 1450 St. Cuthbert (Surtees) 4313 Þere myght na thing thaim stem.
  • 1713 Steele Englishm. No. 28. 184 They were able to stem the proceedings of the Crown when they pleased.

Other sayings may have contributed to the confusion on the usage of stem meaning "make headway against" such as the following from the OED:

To stem one's course:

• to make one's way against difficulties (rare)

  • 1826 M. W. Shelley Last Man II. 36 Slowly and sadly I stemned [sic] my course from among the heaps of slain.

The Phrase Finder cites the followin usage:

Stem the tide:

• Arrest or divert a trend that is running against one's interests.

  • ... Fred A. Paley, writing in 1855 on the tragedies of Ayschylus, said: "Aristophanes evidently saw the trend that was setting in favour of the new candidate for scenic supremacy, and he vainly tried to stem the tide by the barrier of his ridicule." From The Dictionary of Cliches by James Rogers

Stem the tide:

• Stop the course of a trend or tendency, as in It is not easy to stem the tide of public opinion. This idiom uses stem in the sense of "stop" or "restrain." [Mid-1800s] From The American Heritage® Dictionary of Idioms by Christine Ammer

Also from the following definitions it appears that the more common meaning is to stop, to hold back, but instances of the other connotation con be found probably because of the close analogy that the two meanings carry as shown here:

• The general, yet incorrect, use of “stem the tide” is to deflect a serious problem, but tides can’t be deflected. A stem is the upright beam, at the fore of the ship where the hull timbers form the prow. The nautical maneuver against a surging tide is the same as against an angry sea. The ship is turned to stem the onslaught. To “stem the tide” means that to overcome serious problems, you must face them head-on.

So to answer point 2 and 3 I think that the original and more common meaning of "stem the tide" is to stop, to hold back (something).

As for early literal usage:

• (trans.) Of a vessel, a navigator: To urge the stem against, make headway against (a tide, current, gale, etc.). Hence of a swimmer, a flying bird, and the like: To make headway against (water or wind), to breast (the waves, the air).

  • 1593 Shakes. 3 Hen. VI, ii. vi. 36 As doth a Saile, fill'd with a fretting Gust, Command an Argosie to stemme the Waues. -

  • 1654 Whitlock Zootomia 27 He that would stemme the Tyde, had need of a good Gale. -

Solution 2:

There have been two very good and useful good pieces of research user66974 and Sven Yorg and Christine, who asked the question in the first place. I just have a point of two to add, in case they are useful.

The origin of this expression go back, via old English to Saxon and the Teutonic family of languages, as Etymonline itself makes clear. I suggest we start with the noun (though whether a word starts from noun or verb is difficult to determine). It means

Old English stemn, stefn "stem of a plant, trunk of a tree," also "either end-post of a ship," from Proto-Germanic *stamniz (source also of Old Saxon stamm, Old Norse stafn "stem of a ship;" Danish stamme, Swedish stam "trunk of a tree;" Old High German stam, German Stamm), from suffixed form of PIE root *sta- "to stand, make or be firm."

It seems to me that the botanical meaning is more likely to precede the nautical than vice versa. It is very easy to see how (by an analogy) the 'stem' of a ship comes to be called after the stem of a plant (especially the trunk of a tree).

The citation for the first of the two meanings of the teutonic versions of the verb points to the Early to late 14C CE. The verb is given as

"to hold back," early 14c., from a Scandinavian source, such as Old Norse stemma "to stop, dam up; be stopped, abate," from Proto-Germanic *stamjan (source also of Swedish stämma, Old Saxon stemmian, Middle Dutch stemon, German stemmen "stop, resist, oppose"), from PIE root *stem- "to strike against something" (source also of Lithuanian stumiu, stumti "thrust, push"). Not connected to stem (n.). Related: Stemmed; stemming. Phrase to stem the tide is literally "to hold back the tide," but often is confused with stem (v.2) "make headway against."

I can imagine a good argument in favour of the nautical meaning as being the earlier. It is easy to see how the force of tides in the Baltic and North Seas were a major challenge for the seamen of those times. But how did the idea of 'holding back' a tide would get to connote 'making headway against it? It is so tempting to trace it back to the noun and its connection with the 'stem' of a ship. That is what makes the headway. But there is a reasonable pathway, at least, from the idea of stopping or 'overcoming' to making headway. It very tempting to think that the noun and verb must in some way be connected, and may well be.

But in the absence of more written evidence, this is probably as far as we can get.