means An idea, notion, or product of mental activity — the thing your mind produces when it considers, reasons, remembers, or imagines.

from From Old English thoht (also gethoht), a noun built straight off the verb thencan, 'to think' — the same family that gives us 'think' and 'thank' (yes, gratitude and cognition are distant relatives, both rooted in the idea of holding something in mind). It traces back through Proto-Germanic *thankaz to a Proto-Indo-European root *tong-, 'to think, feel.' The gnarled spelling with -ought is a fossil: that 'gh' once marked a throaty sound English speakers stopped pronouncing centuries ago, leaving the letters behind like footprints in dried mud.