late 16th cent.: diminutive of Jock. Originally the name for an ordinary man, lad, or underling, the word came to mean 'mounted courier', hence the current sense (late 17th cent.). Another early use 'horse-dealer' (long a byword for dishonesty) probably gave rise to the verb sense 'manipulate', whereas the main verb sense probably relates to the behaviour of jockeys manoeuvring for an advantageous position during a race
