American variant spelling of Riley, itself from the Irish Raghallaigh (courageous); the -ee spelling is a softer, more consciously feminine version that emerged in US naming culture in the 1990s.
Nicknames
ry
Vibe
gentle
How it ages.
The -ee spelling signals its era; the original Riley ages better and more gender-neutrally.
The cultural moment.
Peaked in the US around 2010-2015; currently declining in favour of the Riley spelling.