lag vs put behind bars

lag is a noun but put behind bars is not a noun.

Word	Noun	Adjective	Verb	Adverb
lag	Yes	No	Yes	No
put behind bars	No	No	Yes	No

As verbs, lag and put behind bars are synonyms defined as:

Other synonyms of lag include gaol, immure, imprison, incarcerate, jail, jug, put away, remand.

lag (noun)	put behind bars (noun)
the act of slowing down or falling behind
one of several thin slats of wood forming the sides of a barrel or bucket
the time between one event, process, or period and another

lag (verb)	put behind bars (verb)
throw or pitch at a mark, as with coins	lock up or confine, in or as in a jail
cover with lagging to prevent heat loss
hang (back) or fall (behind) in movement, progress, development, etc.
lock up or confine, in or as in a jail