Present participle of elegise; the act of composing or expressing an elegy; mourning in poetic form.
From elegise (elegy + -ise) plus the present participle suffix -ing. The -ing form shows ongoing action or the gerund (noun) form of the verb.
Adding -ing to verbs is one of the oldest patterns in English—it goes back over a thousand years—so elegising sounds both modern and ancient at the same time.
Complete word intelligence in one call. Free tier — 50 lookups/day.