I. ˈəp-ˌsīd noun
Etymology: up (II) + side (I)
Date: 1927
1. : an upward trend (as of prices)
2.
a. : a positive aspect
b. : promise , potential
a young star with lots of upside
II. ˈəp-ˈsīd preposition
Etymology: perhaps from up (I) + -side (as in alongside )
Date: 1929
: up on or against the side of
layin' in this death cell, writin' my time upside the wall — Lonnie Johnson
smacked him upside the head