naturally the waw is only seen in a nominative position. in accusative and genitive positions the words in a non-diacritic would look the same. Is amr a hindu name as well? or is it of a different spellin?
actually harakaat were added quite very late in arabic and only for ajamis, therefore to distinguish between `umar and `amr a slient waw is written at the end with `amr
`umar and `amr are both proper (as in correct) names. the second khalifa is sayyiduna `umar raDiyallahu `anhu written عمر in arabic. a few sahaba are named `amr among whom `amr ibn al-`aS radiyallahu anhu is very prominent. some people in the subcontinent mispronounce this name as `amru or `umru because of the additional silent waw written in front (probably to differentiate) between the two names. in arabic: عمرو ---- the name of RasulAllah's sallallahu `alayhi wa sallam worst enemy among the quraysh, abu jahl, was also named `amr: `amr ibn hisham. RasulAllah sallallahu `alayhi wa sallam prayed: 'allahumma a'iyizzi'l islam bi `umar ibn al-khattab aw bi `amr ibn hisham' / o Allah, give strength to islam by the islam of `umar ibn al-khattab or `amr ibn hisham (abu jahl). ----- Allah ta'ala knows best.