köken: Inherited from Old Spanish sotil (“thin; subtle”), inherited from Latin subtīlis. Although the Old Spanish term was inherited, and was often used concretely ("thin, fine"), since the early modern period it has been increasingly relegated to abstract uses. The vowel change o > u may be due either to the following i, or due to the influence of the Latin etymon.
aile: sutileza, sutilmente
La diferencia sutil entre un vocablo y otro juega un papel importante.
köken: Adapted borrowing of Latin subtīlis + -ny. Earlier, as expected, subtylny. The current form is hypercorrect – when the accepted pronunciation of é was changing from y to e, the word was reinterpreted as subtélny, and the new y-less form was reinforced by adjectives in -telny.