From Japanese
幸 (yuki) meaning "happiness" or
雪 (yuki) meaning "snow" combined with
子 (ko) meaning "child". Alternatively, it can come from
由 (yu) meaning "reason, cause" with
喜 (ki) meaning "joy" or
貴 (ki) meaning "valuable" combined with
子 (ko) meaning "child". Other kanji combinations can also form this name.