dilate: [14] Latin lātus meant ‘wide’ (it probably came from an earlier *stlātos, represented in Church Slavonic stilati ‘spread out’, and has given English latitude). It was used with the prefix dis- ‘apart’ to form the verb dīlātāre ‘expand, extend’, which English acquired via Old French dilater. The word has two English nominal derivatives: dilatation [14], from late Latin dīlātātiō, now mainly restricted to medical contexts, and dilation [15], an English formation. => latitude
dilate (v.)
late 14c., from Old French dilater, from Late Latin dilatare "make wider, enlarge," from dis- "apart" (see dis-) + latus "wide" (see latitude). Related: Dilated; dilating.