A verb in The Etymologies of the 1930s appearing as tamin “I tap” under the root ᴹ√TAM “knock” (Ety/TAM). See the entry ᴹQ. ton- for other similar “tap, knock” verbs.
Qenya
ton-
verb. to tap, knock
tam-
verb. to tap
Beware, older languages below! The languages below were invented during Tolkien's earlier period and should be used with caution. Remember to never, ever mix words from different languages!
A verb in the Quenya Verbal System of 1948 derived from the root ᴹ√TON “tap, knock” and so presumably with the same meaning (PE22/103). It replaced a verb tun- from a deleted root ᴹ√TUN “tap, knock, touch (with the fingers)” (PE22/103).
Conceptual Development: A possible precursor ᴱQ. otto- “knock” appeared in the Qenya Lexicon of the 1910s under the early root ᴱ√OTO of the same meaning (QL/71). This in turn may have become ᴹQ. tam- “to tap” and ᴹQ. tamba- “to knock, keep on knocking” from The Etymologies of the 1930s under the root ᴹ√TAM “knock” (Ety/TAM). Finally there are some roots √TOK and √NOK from 1959-60 notes used of “non-resonant sounds” but with no derivatives (PE17/138).
Neo-Quenya: For purposes of Neo-Quenya, I would use the later attested verbs, but I would assume tam- is for a lighter “tap” vs. ton- for a deeper (single) “knock”, whereas tamba- is for repeated knocking or tapping.