tessera

[tes-er-uh] /ˈtɛs ər ə/
noun, plural tesserae
[tes-uh-ree] /ˈtɛs əˌri/ (Show IPA)
1.
one of the small pieces used in mosaic work.
2.
a small square of bone, wood, or the like, used in ancient times as a token, tally, ticket, etc.
Origin
1640-50; < Latin < Greek (Ionic) tésseres four
British Dictionary definitions for tessera

tessera

/ˈtɛsərə/
noun (pl) -serae (-səˌriː)
1.
a small square tile of stone, glass, etc, used in mosaics
2.
a die, tally, etc, used in classical times, made of bone or wood
Derived Forms
tesseral, adjective
Word Origin
C17: from Latin, from Ionic Greek tesseres four
Word Origin and History for tessera
n.

plural tesserae, 1650s, from Latin tessera, from Ionic Greek tesseres (Attic tessares) "four" (see four).