assimilated form of com- "with, together" before stems beginning in -l-. In early Latin, com- was assimilated to these as con-, but col- later also was used. Latin words in coll- became col- in Old French and thus in early Middle English but were altered back to coll- with the revival of learning.
"resembling a line, of or pertaining to lines," 1640s, from French linéaire, from Latin linearis "belonging to a line," from linea "string, line" (see line (n.)). Essentially the same word as lineal; "in Latin linearis the original suffix -alis was changed to -aris by dissimilation, but in Late Latin this rule was no longer productive and the formation or re-formation in -alis remained unchanged." [Barnhart].
As "involving the use of lines" from 1840, hence Linear A, Linear B, names given (1902-3) to two related forms of linear Minoan writing discovered 1894-1901 in Crete by Sir Arthur Evans and long defying translation. It is used there in opposition to pictographic.
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<a href="https://www.etymonline.com/word/collinear">Etymology of collinear by etymonline</a>
Harper, D. (n.d.). Etymology of collinear. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/collinear