In browsing tatting shuttles on eBay I came across this description
THIS IS A NICE SEWING TOOL CALLED A TATTING SHUTTLE. THESE ARE USED TO ASSIST IN THE SEWING PROCESS BY HOLDING THREAD WHILE EMBROIDERING OR SIMILAR TASKS. SHUTTLE MEASURES 3" LONG.
This may in fact be true. People may use shuttles to hold thread while embroidering. I wouldn't know. But it amuses me, this being the main thing used to explain a shuttle. Perhaps we could explain a tatting shuttle better by saying that it is used for, oh, I don't know, .... tatting?