lower (v.1) Look up lower at Dictionary.com
c.1600, "to descend, sink," from lower (adj.), from Middle English lahghere (c.1200), comparative of low (adj.). Transitive meaning "to let down, to cause to descend" attested from 1650s. Related: Lowered; lowering. In the sense "to cause to descend" the simple verb low (Middle English lahghenn, c.1200) was in use into the 18c.
lower (v.2) Look up lower at Dictionary.com
"to look dark and threatening," also lour, Middle English louren, luren "to frown" (early 13c.), "to lurk" (mid-15c.), from Old English *luran or from its cognates, Middle Low German luren, Middle Dutch loeren "lie in wait." Form perhaps assimilated to lower (1). Related: Lowered; lowering.
lower (adj.) Look up lower at Dictionary.com
c.1200, lahre, comparative of lah (see low (adj.)).