Bloody and deceitful men = men of bloods and deceit. Genitive of Character. Hebrew bloods = great bloodshed.
half their days. Referring to Absalom's untimely death.
trust = confide. Hebrew. batah.App-69.
To the chief Musician. See App-64.
upon = relating to.
Jonath-elem-rechokim = The dove of the distant Terebinths. App-65. A pictorial description of David in the wilderness, fleeing from Absalom. Compare verses: Psa_55:6-8; and the word hamah = to coo (as a dove). See note on "cry aloud" in Psa_55:17.