overcareless

Etymology tree
Proto-Indo-European *úp
Proto-Indo-European *-er
Proto-Indo-European *upér
Proto-Germanic *uber
Old English ofer-
Middle English over-
English over-
Proto-Indo-European *ǵeh₂r-der.
Proto-Germanic *karō
Proto-West Germanic *karu
Old English caru
Proto-Indo-European *lewh₁-
Proto-Indo-European *lewHs-der.
Proto-Germanic *leusaną
Proto-Germanic *lausaz
Proto-Germanic *-lausaz
Proto-West Germanic *-laus
Old English -lēas
Old English carlēas
Middle English careles
English careless
English overcareless
From over- + careless.