ya, the verbage comes from vinyl records.
LP = Limited Play ; EP = Extended Play
EP is now just means it is more songs than a single but not enough songs to considered a full length album.
You are showing your (lack of) age. LP was Long Play - usually 12 inch 33 1/3 records (as opposed to the 7 inch 45 singles and the old 10 inch 78s. )
EPs (which you correctly call extended plays) were originally 45s engineered to have 2 songs per side instead of the usual 1.