1540s, justle, "to knock against," formed from jousten (see joust) + frequentative suffix -tle. The usual spelling 17c.-18c. was justle. An earlier meaning of the word was "to have sex with" (c.1400). Meaning "to contend for the best position or place" is from 1610s. Related: Jostled; jostling. As a noun from c.1600.
To pick pockets: a junkie vocation known as ''jostling''/ always looking for cats who were down there jostling (1929+)