From Sanskrit ओष्ठ (oṣṭha) + अमृत (amṛta) + -ము (-mu).
ఓష్ఠామృతము • (ōṣṭhāmr̥tamu) ? (plural ఓష్ఠామృతములు)
"ఓష్ఠము" in Charles Philip Brown (1903) A Telugu-English dictionary, Madras: Promoting Christian Knowledge, page 220