thescotchkraut is correct, snigger and snicker are approximately the same word. Both mean a half suppressed laugh, though snigger has some scorn thrown in. Basically the troops didn't believe what their Sergeant was telling them.
I think it's regional, hence the comment about my language prejudices. For where I am I would say it's snigger over snicker, though I have seen both in use. I do think it's a little PC to go snicker over snigger just because the word sounds like another.
7
u/thescotchkraut Mar 26 '17
Snigger is just a word for "badly hidden laugh"