For most of your period, the official state language of Scotland was Scots, not Gaelic.

http://www.educationscotland.gov.uk/knowledgeoflanguage/scots/introducingscots/history/index.asp

Scots was a language very similar to English. Originally virtually identical, or a dialect of old English, though it diverged somewhat from English during the course of the Middle Ages. After 1603, the Union of Crowns, between Scotland and England, Scots and English began to converge, rather than diverge, until today, English is the primary language in Scotland (though some people still speak Scots at home).

Before Old English, and then Scots, came into Scotland, the two original languages are thought to have been Brythonic (similar to the Celtic languages spoken in England before (and during) the Roman occupation, and Pictish (about which very little is known. It is mostly thought today to have been a Celtic language, but some have speculated that it might have been a pre-Celtic language).

Scottish Gaelic is thought to have been brought to Scotland in late Roman times by settlers from Ireland. It replaced Pictish in much of Highland Scotland (during roughly the same era in which Scots was replacing Brythonic in Lowland Scotland). Scottish Gaelic is only spoken by about 1% of the population of Scotland today.

The court language of Scotland in the Early Middle Ages was Scottish Gaelic, but by 1100, (or very soon thereafter) had mostly switched to Scots.

As Scots and English were close relations, I would expect that much military terminology between the two countries was similar (though probably not identical).

Unfortunately, I do not know enough about the two military terminologies to be more specific. Perhaps someone else who is more expert on this will comment.

Jordan Fantosme's Chronicle of the War between the English and the Scots in 1173 and 1174 is, aside from being one of the earliest examples of vernacular French verse, a first-hand account of the titular war written by a Northumbrian cleric with friends on both sides of the border.

What's clear in the Chronicle is that the Scottish court at the the time under King William was attempting to be as Norman as possible. This was largely the legacy of King David I, who had grown up at King Henry I's court in England, and wanted to recreate that kingdom in Scotland, and so had implemented military and social modernisations and invited in Norman and Flemish knights from Europe.

According to Jordan Fantosme, the core of William's army that invades England in 1173 and 1174 is essentially a smaller mirror of the English army it would be facing, with a contingent of mounted knights from France, Flanders and Scotland, supported by sergeants, archers and even siege engineers. Around this core, however, was a levy of 'Pictish' and highland tribes who were apparently guilty of the most abhorrent and uncivilised behaviour, were poorly armed and badly disciplined, but ferocious in combat.