late 14c., "intersection of two straight lines; division of a scale;" from Old French section or directly from Latin sectionem (nominative sectio) "a cutting, cutting off, division," noun of action from past participle stem of secare "to cut," from PIE root *sek- "to cut." From 1550s as "act of cutting or dividing." Meaning "subdivision of a written work, statute, etc." is from 1570s. Meaning "a part cut off from the rest" is from early 15c.
"divide into sections," 1819, from section (n.). Related: Sectioned; sectioning.