jag

Concise Oxford English Dictionary © 2008 Oxford University Press:
jag1

▶verb (jags, jagging, jagged) stab, pierce, or prick. ▶noun

• 1 a sharp projection.

• 2 chiefly Scottish an injection.

– derivatives
jagger noun.

– origin ME: perh. symbolic of sudden movement or unevenness (cf. jam1 and rag1).

Concise Oxford English Dictionary © 2008 Oxford University Press:
jag2

▶noun

• 1 informal, chiefly N. Amer. a bout of unrestrained activity or emotion: a crying jag.

• 2 dialect a bundle.

– origin C16 (in sense ‘a load of hay or wood’, later ‘as much alcohol as one can hold’): of unknown origin.