imitative of laughter, Old English.
Ha ha and he he getacniað hlehter on leden and on englisc. [Ælfric, "Grammar," c.1000]
He says to me: 'That guard'll stop any fire I ever saw,' and I got right back at him—he-he!
I shouldn't have been a Napoleon, but I might have been a major, he-he!
I fancy I really am: I tell you these things for nothing and don't even expect a reward for it, he-he!
She turned into Regent Street and another 'he-he' floated back.
I met him up here a little ways just now, and he was so sober he remembered to pay me that ten I lent him t' other day—he-he!
By granny, I'm going to plug m' ears good with cotton when it comes off—he-he!
If they cast themselves upon the beds, they are mine, he-he!
But never mind, he'll make his mark someday—finger mark, you know, he-he!
It's not merely that he has nowhere to run to, he is psychologically unable to escape me, he-he!
Then he-he push her head back-like, so's 'ee c-could get at her mouth, and then Dic he-he ups and knocks him d-down.