metric (n.) Look up metric at Dictionary.com
"science of versification," 1760, from Greek he metrike "prosody," plural of metron "meter, a verse; that by which anything is measured; measure, length, size, limit, proportion" (see meter (n.2)).
metric (adj.) Look up metric at Dictionary.com
"pertaining to the system of measures based on the meter," 1855, from French métrique, from mèter (see meter (n.2)). In this sense, metrical is attested from 1797.