First thought was "bulge". Then I went on to look at what the guy was wearing, and thought that the leather strap going under his arm would be mighty uncomfortable, especially when it makes his way under his armpit and starts chafing, so he's gotta move it back from out of his armpit, but then you'd just be like *sigh* "this is just gonna go into my armpit again within the next 10 minutes and I'm gonna have to move it back out again".