Something is “yay” big

Question

I have heard expressions like "It was yay big" or "It was yay by yay." a couple of times now, always accompanied by a gesture indicating the size of something. Does anybody know where this word comes from? Can it be used in other situations? Is it older or newer than the word that? If it's of any help it is frequent in the UK.

Edit: I obviously tried searching for it myself but my results seem to be dominated by the word yay as an expression of joy. I assume the two are completely unrelated.

Answer 1

The expression is actually (or originally) "yea big" or "yea high" where yea essentially means this.

Wiktionary has an entry for yea:

Thus, so (now often accompanied by a hand gesture)

The pony was yea high.

Unfortunately, I haven't been able to find definitions for this word (with this sense) in any other dictionaries online.

Yay is most likely a corruption of yea.

Answer 2

The OED records it as ‘U.S. slang’ and suggests it is probably from yea, yea being ‘a word used to express affirmation or assent'.

The OED’s first recorded use is this from Wentworth and Flexner’s 1960 ‘Dictionary of American Slang’:

Yea big, yea high, 1. This big, or this high, accompanied with the spreading of the hands to indicate the size; very large, or high, overwhelmingly large or tall. 2. Not very big or high.

Answer 3

NOAD defines yay as follows:

yay (adv.) informal
(with adjectives of measure) so; to this extent : I knew him when he was yay big.
ORIGIN 1960s: probably a variant of the adverb yea.

NOAD's entry for yea includes:

used for emphasis, esp. to introduce a stronger or more accurate word than one just used : he was full, yea, crammed with anxieties.