§ Hathaldir (TI:227,240)
The Elf who meets the fellowship at Lórien was originally named Haldir; this was changed to Hathaldir and then back again to Haldir. ’Hathaldir the Young’ also appears in the early Silmarillion as a companion of Barahir (LR:282). Later on, we encounter a Númenorean named Hatholdir (UT:173); and Hathol ’the Axe’, a descendant of Marach (WJ:234).
In The Etymologies we find N. hathel < syatsēla, syatsĕla ’broadsword or axe-blade’, formed with the ending -la denoting an object from syadsē > syatsē ’cleft, gash’ (SYAD-). #Hathal would then require *syad-sa-la > *syatsala with a noun derivational ending -sā, -să instead of -sē, -sĕ. Such an ending occurs in the derivation of Q. apsa ’cooked food, meat’ (AP-) for example. Hathol could be from *syatsāla with long ā > au > o.
The second element in the name is clearly N. †dîr ’male, man (elf, mortal, or of other speaking race)’ surviving chiefly in proper names (DER-).