stubborn 艮 (281a) + swallow (779a) = since 既

One of the strokes of “stubborn” is missing here (see 281a). This is the form which “stubborn” takes whenever there is something else to its right in a composite character.

The elderly man stubbornly refused to swallow the pills, saying, “Since I’ve never swallowed a pill, I’m not going to start now.” / [No pronunciation needed]