A prefix meaning “easy” or “easily” appearing in Definitive Linguistic Notes (DLN) from 1959 and based on the root √ATHA (PE17/148). Tolkien gave two examples of its use: athgar “easy (easy to do)” = ath + √KAR “do” and athgen “easily seen” = ath + √KEN “see”. These adjectives seem to be similar to the negative quasi-participles like úgar “(generally) idle = *not doing” seen in other notes from around 1959 (PE17/144), where the prefixed verb stem functions as an (aorist) participle. Presumably such quasi-participles are neither active or passive, and so assume a meaning based on the prefix: ath- “easy” functions passively (the thing done), ú- “not” functions actively (the person doing).

Conceptual Development: In a rejected page from the same set of notes, Tolkien had rhae “easy” derived from the root √SRA(YA) of the same meaning (PE17/172). But Tolkien seems to have altered the root to √SRAG “difficult” and √RAY “smile”.