Here are some synonyms for puerile:
* childish
* immature
* juvenile
* infantile
* silly
* frivolous
* nonsensical
* trivial
Examples:
* "His puerile jokes made everyone groan."
* "The argument was puerile and pointless."
* "The film's plot was so puerile it was hard to take seriously."
Origin:
The word "puerile" comes from the Latin word "puer", meaning "boy" or "child".