An Etymological Dictionary of Astronomy and Astrophysics

The highest point or part. The higher end of anything on a slope.

Etymology (EN): M.E., O.E. top “summit, crest, tuft;” cf. O.N. toppr “tuft of hair,” O.Fris. top “tuft,” O.Du. topp, Du. top, O.H.G. zopf “end, tip, tuft of hair,” Ger. Zopf “tuft of hair.”

Etymology (PE): Bâlâ “up, above, high, elevated, height” (variants boland “high, tall, elevated, sublime,” borz “height, magnitude” (it occurs also in the name of the mountain chain Alborz),
Laki dialect berg “hill, mountain;”
Mid.Pers. buland “high;” O.Pers. baršan- “height;” Av. barəz- “high, mount,” barezan- “height;” cf. Skt. bhrant- “high;” L. fortis “strong” (Fr. and E. force); O.E. burg, burh “castle, fortified place,” from P.Gmc. *burgs “fortress;” Ger. Burg “castle,” Goth. baurgs “city,” E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- “high.”