In Irish when you are talking directly to someone dear to you, EG, your partner or child, you could address them as, 'A chuisle' = 'Love' or 'darling', but if you are speaking about them to someone else you might refer to him/her as 'mo chuisle' = my dear/darling. The Irish people switched languages but brought this term and many others such as 'a ghillín', 'a stór', 'a chroí', 'a mhúirnín', etc ] over into their version of English and spread them abroad. Many of Irish or part-Irish descent use them without knowing the literal meaning and I reckon that's great.