1. English, via Old French Lucie, from Latin Lucia, itself derived from lux, "light".

It may be that in some cases Lucy is a pet name for Lucinda [q.v.] but there is no direct connection between these names apart from usage.

In old documents in Latin, Lucia may be used for Lucy, with appropriate case endings.

2. Lucy is used as an Anglicised form of the Irish Gaelic name Luíseach [q.v.] and is equivalent to the Scottish Gaelic name Liùsaidh.