肼 is a chemistry-domain character — the Chinese name for hydrazine, a colorless flammable liquid (NH2-NH2) used in rocket propellants and pharmaceuticals. The character was coined in modern times for this compound; it has no other common usage.
memory
Radical 月 (flesh/organ, common in body/biological terms) + phonetic 井 (jǐng, 'well'). The 井 gives both shape and sound — picture a chemistry well of toxic liquid.
