The term 'Immeasurably Long Time' can be represented by two crossword solutions, AEON (4 letters) and EON (3 letters). An AEON is an immeasurably long period of time, often associated with eternity or the concept of forever. It is derived from the Greek word aion, which means age, eternity, or a period of time. An EON is also an immeasurably long period of time, but it is slightly shorter than an AEON. It is derived from the Greek word aionios, which means lasting for an age. Both terms are used to describe a period of time that is so long that it cannot be measured.