The phonetic/phonemic sequence 'o-m' appears over 200 times in the 1st maNDala of Rgveda, but not even once as a syllable.
By far the most instances are in the word 'soma' (so-ma), and its oblique case (e.g. locative singular: some). Also 'stoma' and 'goma' are quite common... A tvetA\` ni ShI\'da\`tendra\'ma\`bhi pra gA\'yata | sakhA\'ya\` stoma\'vAhasaH || 1\.005\.01 pu\`rU\`tama\'M purU\`NAmIshA\'na\`M vAryA\'NAm | indra\`M some\` sachA\' su\`te || 1\.005\.02 sa ghA\' no\` yoga\` A bhu\'va\`tsa rA\`ye sa pura\'MdhyAm | gama\`dvAje\'bhi\`rA sa na\'H || 1\.005\.03 yasya\' sa\`Msthe na vR^i\`Nvate\` harI\' sa\`matsu\` shatra\'vaH | tasmA\` indrA\'ya gAyata || 1\.005\.04 su\`ta\`pAvne\' su\`tA i\`me shucha\'yo yanti vI\`taye\' | somA\'so\` dadhyA\'shiraH || 1\.005\.05 tvaM su\`tasya\' pI\`taye\' sa\`dyo vR^i\`ddho a\'jAyathAH | indra\` jyaiShThyA\'ya sukrato || 1\.005\.06 A tvA\' vishantvA\`shava\`H somA\'sa indra girvaNaH | shaM te\' santu\` prache\'tase || 1\.005\.07 tvAM stomA\' avIvR^idha\`ntvAmu\`kthA sha\'takrato | tvAM va\'rdhantu no\` gira\'H || 1\.005\.08 akShi\'totiH sanedi\`maM vAja\`mindra\'H saha\`sriNa\'m | yasmi\`nvishvA\'ni\` pauMsyA\' || 1\.005\.09 mA no\` martA\' a\`bhi dru\'hanta\`nUnA\'mindra girvaNaH | IshA\'no yavayA va\`dham || 1\.005\.10
