[DonaldFisk]

According to Wikipedia and Wiktionary its etymology is English. I also checked with A Pronouncing and Etymological Dictionary of the Gaelic Language by Malcolm McLennan, which has "tocsaid, n. f. a hogshead ; fr. the Eng." Gaelic for barrel is "baraille".

The Irish for hogshead and barrel can be found at https://www.focloir.ie

[FooHentai]

https://en.wiktionary.org/wiki/togsaid

Perhaps the Gaelic word for barrel somehow came from the English measurement hogshead, but more likely that it was spoken Gaelic for barrel overheard and adopted by English speaking stevedores.

[DonaldFisk]

The main problem with that is that the first recorded occurrence of the word was in Middle English in 1390: https://quod.lib.umich.edu/m/middle-english-dictionary/dicti... i.e. before (Scottish) Gaelic diverged from Irish. If the word had a Middle Irish origin predating this, it would be shared by its descendants in both modern languages. But the Irish word is oigiséad (m), and the Gaelic word is tocsaid (f). Different genders, and Irish dropped the h sound, which (after lenition) Gaelic preserved. So the word must have arrived in Irish and Gaelic independently, presumably from Modern or Late Middle English after Gaelic and Irish diverged into separate languages.

The other problem is that there is no known Irish etymology for either tocsaid or oigiséad, or Malcolm McLennan would have included it in his faclair, but there is a plausible English one. Other Germanic languages (Dutch, German, Danish, Swedish) have variants of ox-head. Whether it originated in one of those languages or in English is disputed.