Sound
Decent, reliable, good. Used as an adjective for a person of generally trustworthy character ('he's a sound fella') and, more distinctively, as a single-word reply meaning thanks, no bother, or that's grand. Distinct from the standard English senses (a sound argument, a sound sleep).
Etymology
A semantic shift from older English 'sound' (whole, intact, well-founded), from Old English 'sund' (healthy). Standard English kept the older senses (a sound horse, a sound bridge); Hiberno-English flexed the word into an everyday compliment for a person's character and an all-purpose acknowledgement. The single-word reply use - just 'sound', on its own - is documented from the mid-twentieth century onwards and is the most distinctively Irish form.
In a sentence
Cheers - sound out. - a casual thanks
Don't worry about it - that's sound. - an easy reassurance
Historical notes
Sound is the Irish English speaker's go-to mild compliment, working at every register. A stranger who lets you in at a junction earns a 'sound'. A friend who's covered for you is 'sound out'. A person of generally decent character is 'a sound fella'. The single-word reply does the communicative work that English speakers elsewhere split between 'thanks', 'no problem', and 'cool' - all three are sound. Like 'grand', it sounds laconic to outsiders but does precise emotional work for the speaker.
Sources
- Hickey, Raymond. Irish English: History and Present-Day Forms. Cambridge University Press, 2007. · academic
- Oxford English Dictionary, entry sound adj. (sense 'in good condition, reliable'). · dictionary