"Say that again, Iain. I have a little Gaelic."
Translation:Can sin a-rithist, Iain. Tha beagan Gàidhlig agam.
beagan is a noun meaning a little/a few, so you have a little of Gaelic. The word order is possessed + possessor, as in e.g. taigh bodaich 'the house of an old man/an old man's house'. Many other nouns that you have a little of will be visibly inflected in the genitive case to mark this too, like beagan airgid 'a little money' from airgead 'money' or beagan sheachdainean 'a few weeks' from seachdain week, but Gàidhlig never changes.