congruity (n.)

"agreement between things, harmony," late 14c., from Old French congruité "relevance, appropriateness" or directly from Late Latin congruitatem (nominative congruens) "agreement," from congruus "suitable, agreeing," from congruere "to agree, correspond with," literally "to come together," from assimilated form of com "with, together" (see con-) + a lost verb *gruere, *ruere "fall, rush" (see congruent).