I've read that this translates literally as "my pulse", which seems like a very pleasant thing to call someone.
Somewhat later, ryano was kind enough to confirm my guess, and to inform me further; these are his words:
You'd normally say "a chuisle, a chroí" (pron. "acushla acree"), which means, "My pulse, my heart", or "a chuisle mo chroí", which means "Pulse of my heart".