The word "瞻前顾后" is formed by the conjunction of two parallel verb-phrase components: "瞻前" (瞻 meaning "to look forward" paired with 前 meaning "front") and "顾后" (顾 meaning "to look back" paired with 后 meaning "behind"). This creates a literal, symmetrical compound describing the physical act of looking both ahead and backward, which directly gives rise to the idiomatic meaning of being overly cautious or indecisive by considering every possible angle.