There is a Hebrew stem k-n-h. Means mourning over a dead person or a tragedy, like the destruction of the Temple and Jerusalem. Women who were professional dirgers were called m'qon'not. Is there any connection between this word and the Irish keening?

Highly unlikely. This sort of linguistic coincidence happens all the time. However, once again I will bow to the greater wisdom of zmjezhd or goofy.

I agree with Faldage. "keen" is from Irish Gaelic "caoin-im" to wail. McBain's Etymological Dictionary of the Gaelic Language connects it to Proto-Indo-European "*kwei-" to hiss, whistle, as in English "whine".

Is keening similar to holding a WAKE?

Listen to the video Anu added to the word, Candy. It's a beautiful lament.:-) I think keening is what is done in many cultures, from high pitched screams to beautiful music. A wake is something else, though there may be keening at a wake.