"Blend of Betty and Lou"
The name Bettylou is commonly a female name from the "English" origin.
Bettylou is a run-together spelling of the two-part American given name Betty Lou, formed from Betty and Lou. Betty is an English diminutive of Elizabeth, and Lou is a short form of Louise or Louis. The joined spelling appears in United States birth records from 1916, which is consistent with a compound of two already established given names rather than a name borrowed whole from another language.
The pronunciation of Bettylou is BET-ee-loo.