[1790–1800; ‹ L senect(ūs) old age (equiv. to senec-, extracted as s. from senex (gen. senis) old man + -tūs abstract n. suffix) + -i- + -tude, on model of plenitude, rectitude, etc.]This word is first recorded in the period 1790–1800. Other words that entered Englishat around the same time include: backhanded, echelon, idealism, methodology, standby-i- is the typical ending of the first element of compounds of Latin words, as -o- is of Greek words, but often used in English with a first element of any origin,if the second element is of Latin origin. Other words that use the affix -i- include: Frenchify, cuneiform