@Luisa_Donato
This
tldp.org/LDP/Linux-Filesystem-
says that the meaning changed when home folders moved:
"In the original Unix implementations, /usr was where the home directories of the users were placed [...]. The name hasn't changed, but it's meaning has narrowed and lengthened from "everything user related" to "user usable programs and data". As such, some people may now refer to this directory as meaning 'User System Resources' and not 'user' as was originally intended."