Talk about Primitive.
I thought Love Me Do was remarkable for only having 19 different words in the whole song.
I Wanna Be Your Man has only 18!
Other contenders are Magical Mystery Tour with 36 words, Don't Let Me Down with 40 and Little Child with a positively verbose 46. But the outright winner is I Want You (She's So Heavy) which has 13 (6 of which are in the title).
Calm down Shakespeare!