immo, "same one, self" (VT49:33), general singular reflexive pronoun (covering both the 1st, 2nd, and 3rd person sg.), except where the subject is impersonal, in which case imma is used instead (VT47:37). Hence *tirin immo* "I watch [my]self", tirilyë immo "you watch [your]self", tiris immo "(s)he watches [him/her]self" (but apparently tiris imma** "it watches [it]self").
Quenya
tiris
watch, vigil
Tiristemindon
place name. Minas Tirith
tiris
noun. watch, vigil, ward
tirista
noun. *watch, guard
immo
same one, self
insa
itself
insa *"itself", 3rd person sg. impersonal reflexive pronoun, e.g. *tiris insa "it watches itself" (but apparently the general reflexive pronoun immo may also be used, and it may even be preferable since the cluster ns seems unusual for Quenya). Compare insë, the corresponding personal form.
insë
himself
insë "himself" and "herself", 3rd person sg. personal reflexive pronoun, apparently covering both genders, e.g. *tiris insë "(s)he watches him/herself" (but apparently the general reflexive pronoun immo may also be used, and it may even be preferable since the cluster ns seems unusual for Quenya). Compare insa, the corresponding impersonal form. Insë is derived from earlier imsë, a form that was possibly also used in Quenya (unless "imse" in Tolkien's manuscript is intended as an etymological form only, though it is not asterisked) (VT47:37)
cenda-
watch
cenda- vb. "watch" (not "guard", but observe to gain information), also used = "read". Cenda = also noun "reading", as in sanwecenda "thought-inspection, thought-reading". (VT41:5, PE17:156)
imma
itself
imma *"itself", impersonal reflexive pronoun referring to the "same thing" (VT47:37) as the subject; compare immo.
insa
pronoun. itself
tir-
watch, watch over, guard, heed
tir- vb. "watch, watch over, guard, heed", 1st pers. aorist tirin "I watch", pa.t. tirnë (TIR), imperative tira (VT47:31) or á tirë (PE17:94), future tense tiruva "shall heed" in Markirya (also MC:213, 214); also in CO with pronominal endings: tiruvantes "they will guard it" (tir-uva-nte-s "guard-will-they-it"). The stem also occurs in palantíri (q.v.), Tirion place-name "Great Watchtower", a city of the Elves (SA:tir; in MR:176 the translation is "Watchful City")
tiris (tiriss-), also tirissë, noun "watch, vigil" (LT1:258, QL:93)