Mine:
Girls’ Last Tour Song of Raindrops ED
What’s common on those four? They’re all works of art with very emotional music.
My top favorite is that of A Place Further Than The Universe for personal reasons. I had a fulfilling trip shortly after watching this show for the first time. Hearing the song again/watching the show again made me very, very happy each time.
Your question actually got me curious, so I tried to search for where it came from and it is literally just short for EnDing. Seems a bit silly really. It does provide a nice symmetry with OP though.
Could have something to do with Japanese phonology