"Good night, James."
Translation:Oidhche mhath, a Sheumais.
Most masculine names do, as do many other masc. nouns – when they form genitive by slenderization (eg. a chait mhòir (oh) big cat!, a bhalaich bhig (oh) little boy!).
See Masculine nouns on the Akerbeltz wiki.
This particular vocative (a Sheumais /ə heːmiʃ/), by the way, is the source of the name Hamish in English (so Hamish is just very Gaelic James…).