centigrade adj.

word-forming element meaning "one hundred" or "one hundredth part," used in English from c. 1800, from the French metric system, from Latin centi-, combining form of centum "one hundred" (see hundred).

Proto-Indo-European root meaning "to walk, go." 

It forms all or part of: aggress; aggression; aggressive; centigrade; congress; degrade; degree; degression; digress; digression; egress; gradation; grade; gradual; graduate; grallatorial; gravigrade; ingredient; ingress; plantigrade; progress; progression; regress; regression; retrograde; retrogress; tardigrade; transgress; transgression.

It is the hypothetical source of/evidence for its existence is provided by: Latin gradus "a step, a pace, gait," figuratively "a step toward something, a degree of something rising by stages;" gradi "to walk, step, go;" Lithuanian gridiju, gridyti "to go, wander;" Old Church Slavonic gredo "to come;" Old Irish in-greinn "he pursues."  

1797 in reference to the type of thermometer; 1812 in reference to the scale of temperatures, from the name of Swedish astronomer Anders Celsius (1701-1744) inventor of the centigrade scale in 1742. His family name is a Latinized translation of Högen, the name of the family estate in Sweden, taken as "mound," from Latin celsus "raised, high, lofty, great" (from PIE root *kel- (2) "to be prominent; hill").