Spinner's weasel or clock reel is a mechanical yarn measuring device consisting of a spoked wheel with gears attached to a pointer on a marked face (which looks like a clock) and an internal mechanism which makes a "pop" sound after the desired length of yarn is measured (usually a skein). The pointer allows the spinner to see how close she/he is to reaching a skein. The weasel's gear ratio is usually 40 to 1, and the circumference of the reel is usually two yards, thus producing an 80-yard skein when the weasel pops (after 40 revolutions).
Some reels or skein winders are made without the gear mechanism. They perform the same function, but without the "clock" or pop to aid the spinner in keeping track of the length of thread or yarn produced. A niddy noddy

Niddy noddy

A niddy-noddy is a tool used to make skeins from yarn. It consists of a central bar, with crossbars at each end, offset from each other by 90°. The central bar is generally carved to make it easier to hold. Either one of the crossbars will have a flat edge to allow the skein to slide off, or will...

 is an even simpler version.

The clock reel is a possible source for the word "weasel" in the nursery rhyme

Nursery rhyme

The term nursery rhyme is used for "traditional" poems for young children in Britain and many other countries, but usage only dates from the 19th century and in North America the older ‘Mother Goose Rhymes’ is still often used.-Lullabies:...

 Pop Goes the Weasel

Pop Goes the Weasel

"Pop! Goes the Weasel" is an English language nursery rhyme and singing game. It has a Roud Folk Song Index number of 5249.-Lyrics:There are many different versions of the lyrics to the song...

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