Meaning

adjective involving clever rogues or adventurers especially as in a type of fiction

originFrom picaro (“adventurer, rogue”) + -esque (suffix meaning ‘in the style or manner of’ forming adjectives), modelled after Spanish picaresco (“in the style or manner of a picaro; picaresque”), from pícaro (“rogue”) + -esco (suffix forming adjectives indicating a relation). Compare French picaresque (attested later than the English word), Italian picaresco, Portuguese picaresco.

Etymology from Wiktionary, CC BY-SA 3.0