恐らく

From classical Japanese 'おそる' (osoru, 'to fear, to be afraid') and the particle 'らく' (raku), which indicates conjecture or supposition. The original meaning implied a sense of fear or apprehension about something happening, evolving into the current meaning of expressing a high degree of likelihood or probability, often with a slight nuance of uncertainty or a perceived negative outcome, though this nuance is less prominent in modern usage. It can also be seen as an adverbial form of '恐ろしい' (osoroshii, 'fearful, dreadful').