fall between two stools

Meanings

1. To fit into neither of two categories and, hence, be neglected or fail.
2. To attempt two roles and fail at both, when either could have been accomplished singly.

Etymology

From an old proverb, "Between two stools, one falls to the ground", which dates from 1390. This, in turn, is most likely a translation of the medieval Latin proverb labitur enitens sellis herere duabus ("he falls trying to sit on two seats").