Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
tessella, ae, f. dim. [tessera], a small square piece of stone, a little cube, for pavements, etc., Sen. Q. N. 6, 31, 2; Juv. 11, 132; Plin. 37, 10, 54, § 144; 17, 16, 26, § 120; Inscr. Oreil. 4316.