The sobriquet of Tulkas (S/28), a masculinized form of the adjective astalda “strong” (PE17/115).
Conceptual Development: In the earliest Lost Tales, the sobriquet of Tulkas was ᴱQ. Poldórea (LT1/79), which was the adjective ᴱQ. poldórea “muscular” used as a name (QL/75). The name ᴹQ. Poldórea still appeared in Silmarillion drafts from the 1930s, variously glossed “Strong One” or “Valiant” (SM/79, LR/206). It appeared in The Etymologies as an adjectival form of ᴹQ. poldore “physical strength; might” from the root ᴹ√POL(OD) “physically strong” (Ety/POL).
In later writings, the name Q. Poldórëa appeared in Tolkien’s Words, Phrases and Passages from the Lord of the Rings from the 1950s, along with variants Poldor and Poldorno, where he considered a new meaning for this name as “breaker up of the hard/tough” with its second element coming from the root √DOR “hard” (PE17/181). Ultimately, though the name was changed to Astaldo in Silmarillion revisions from the 1950s-60s (MR/149).
Astaldo noun "the Valiant", a title of Tulkas (Silm, MR:438); replaced Poldórëa.