early 15c., "to copulate" (of wolves, dogs), literally "to range (things) in a line," from Middle French aligner, from Old French alignier "set, lay in line," from à "to" (see ad-) + lignier "to line," from Latin lineare, from linea (see line, n.). Transitive or reflexive sense of "to fall into line" is from 1853. International political sense is attested from 1934. No justification for the French spelling, and aline was an early native form. Related: Aligned; aligning.