well up

verb

well_up: gather; upward motion of water, or as if of water, perhaps from a spring

To gradually or steadily flow upwards or outwards so as to begin to fill or overflow something.
“Oil was welling up out of the borehole.”
“As soon as I heard news of his death, tears started to well up in my eyes.”
To accumulate within one, to the point of overwhelming one.
“Emotion welled up inside me.”
“A barely audible groan welled up in the Captain's throat as the grinning Freedom Fighter circled around behind the helpless American Soldier. The groan sputtered into a strangled, "No… no… don't.... " as Randall felt the juicy tip of the man's tumescent cock jab against his hair-ringed, virgin asshole.”