This came over the transom:
Have you ever weighed in on "suffice" or "suffice it" to say? The "it" drives me nuts, and there seems to be a generational divide over this.
Suffice it to say is a legacy of our old but attenuated friend, the subjunctive mood. It is the subjunctive form of it suffices to say. A fuller version of the expression would be let it suffice to say, but longstanding usage has clipped and inverted it.
Interestingly, contemporary usage has curtailed it further, into suffice to say, so that to some ears, the it sounds wrong. Bryan Garner rates suffice to say in the third edition of Garner’s Modern American Usage as “widely shunned,” but I think he may be mistaken in gauging how widespread the expression has become.
The subjunctive in English survives in such stock expressions. It can also be found in statements contrary to fact (If I were czar of language ...), demands or commands (The czar orders that he buy Garner on Language ), suggestions and proposals (The czar recommends that she be directed to consult Garner before inquiring), and statements of necessity (The czar thinks it essential that they be apprised of shifts in usage).
The subjunctive used to be more widely used, but, Best Beloved, it is not coming back. Would God that you resigned yourself to that.