The word yeast has existed in English for as long as the language has existed. Spellings have varied over time—in Middle English it was yest and in Old English gist or giest—but the word's meaning has remained basically the same for centuries. In its first documented English uses in the 1500s, the adjective yeasty described people or things with a yellowish or frothy appearance similar to the froth that forms on the top of fermented beverages (such as beers or ales). Since then, a number of extended figurative senses of yeasty have surfaced, all of which play in some way or another on the excitable, chemical nature of fermentation, such as by connoting unsettled activity or significant change.