The postal employee had a favorite joke whose punchline was 'Eeyoww!'
He shared the joke with another worker who often sat near him, both of them at their mail cases.
They found moments during each evening's work to repeat the joke in various contexts, struggling time and again to hold back the unrestrained laughter the joke brought them to.
The punchline itself became a shorthand for the whole joke, and it signaled laughs just on its own. Over time, the laughter diminished into chuckles, then into smiles, into a greeting and sometimes an inadvertent mumble below the breath of one or the other of them.
Eventually, the second worker retired.
The day afterward, the first worker, sitting at his customary place, looked forward at his mail case and repeated, to no one in particular, 'Eeyoww! Eeyoww!' A laugh came out with a quick snort. 'Eeyoww!' He repeated, and the tears of laughter ran down his cheeks.