> In Ireland, "colg" [ga] has lost its connection with the meaning
> "sword" [en] in our ordinary speech (never mind the books), for which
> meaning we have chosen a different word. My suspicion is that the same
> loss of meaning probably happened in Scotland and Mann, that "calg" [gd]
> now connects (only?) with the meaning "anger, rage" [en] in the mind of
> Scottish people today, so, if it were shown that all three living
> languages agree on this latter meaning as the main one today (i.e., if
> the same shift happened in all three countries after/before a verifiable
> date), then that is a significant shared semantic shift (if not, it is not).
No, calg in Scotland means bristle/prickle/arista (and calgach means bristly/prickly/aristate). Lus grinn nan dos calgach is still one of our national badges, one sufficiently famed in song that this meaning of calgach isn't going to be lost any time soon, and that probably means that calg won't lose that meaning either.
Of course bristly and prickly in English are both common metaphors for annoyed/irritated; but GD seems not to have done this with calgach.
Colg on the other hand has come to mean wrath/rage, and (less often) glare (I wonder if that came from dropping "suil" from "suil colgach" - wrathful eye?) while colgaich means irritate/annoy; and colgach, although it sometimes means the same as calgach, also sometimes means wrathful/fierce.
So the shift in meaning happened only to one version of the word (colg), and the other (calg) still means a straight pointy thing (but no longer a sword or spear).