Cocksure

[kok-shoo r, -shur] /ˈkɒkˈʃʊər, -ˈʃɜr/

adjective
1.
perfectly or certain; completely confident in one’s own mind:
She was cocksure that she was able to do the job better than anyone else.
2.
too certain; overconfident:
He was so cocksure he would win the election that he didn’t even bother to campaign.
3.
Obsolete. perfectly secure or safe.
/ˌkɒkˈʃʊə; -ˈʃɔː/
adjective
1.
overconfident; arrogant
adj.

1520s, “certain,” from cock (n.1) + sure (adj.). Probably “as assured as a cock.” “The word was originally perfectly dignified, and habitually used in the most solemn connexions” [OED].

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