"Young Girl" was a song performed by Gary Puckett & The Union Gap released in 1968. The song reached #2 on the Billboard Hot 100 and it reached #1 on the UK Singles chart and Cash Box. Apparently - the song is sung from the point of view a man distressed to find out his lover is under an acceptable age. That is what I read on Wikipedia. In the UK, the recording enjoyed a second chart run in 1974, when it peaked at #6. Gary Lewis and the Playboys released a version of the song on their 1968 album, Gary Lewis Now!