"Ironic" vs. "ironical"

Question

Being that this highly related question primarily asked whether ironical is actually a word (and if it is used regionally), I'm interested to know whether there is a difference between it and ironic and what that difference might be.

@steven_desu touched on it in his comment, but I'd like to see a more complete answer to the difference between the two words (if any).
Are they completely interchangeable?
Is one more appropriate in certain situations?

Answer 1

Given these definitions:

ironic:

1. containing or exemplifying irony
2. ironical
3. coincidental; unexpected

ironical:

1. pertaining to, of the nature of, exhibiting, or characterized by irony or mockery
2. using or prone to irony

The only difference I could plausibly assert is that ironical means it uses irony, where ironic means it is an example of irony. That is, this conclusion of this book is ironic. This ironical book is a good, fun read. This ironical author is one of my favorites.

Parenthetically speaking, the inclusion of ironical in the definition of ironic makes sense in this interpretation because an example of irony must by definition use irony.

Answer 2

To the best of my recollection, examples I've seen in literature tend to use "ironical" when applied to speech or behavior, and "ironic" when applied to events or circumstances. (That would loosely follow the pattern of "historical" and "historic.")

Answer 3

Does this help you not use ironical except as an adjective?

http://ngrams.googlelabs.com/graph?content=ironic%2C+ironical&year_start=1800&year_end=2000&corpus=0&smoothing=3

Ironical http://ngrams.googlelabs.com/chart?content=ironic%2Cironical&corpus=0&smoothing=3&year_start=1800&year_end=2000

Answer 4

As a native speaker of English (born in the UK, raised in Hungary), I have never in my life used the word "ironical". I've always felt it is too old-fashioned; meaning the same as "ironic", but far more old-fashioned. I also haven't seen or heard it in contemporary context until just recently. I was reading Casino Royale last week and just at the end of the first chapter I found this:

Then he slept, and with the warmth and humour of his eyes extinguished, his features relapsed into a taciturn mask, ironical, brutal and cold.

However contemporary this text may be, its language is indeed old-fashioned (e.g. the word "taciturn" or that "humour" might as well mean moisture here).

Also, think of the famous Roman grammarian, Gellius, who wrote:

Whether the words necessitudo and necessitas differ from each other in meaning.

1 It is a circumstance decidedly calling for laughter and ridicule, when many grammarians assert that necessitudo and necessitas are unlike and different, in that necessitas is an urgent and compelling force, but necessitudo is a certain right and binding claim of consecrated intimacy, and that this is its only meaning. 2 But just as it makes no difference at all whether you say suavitudo or suavitas (sweetness), acerbitudo or acerbitas (bitterness), acritudo or acritas (sharpness), as Accius wrote in his Neoptolemus,6 in the same way no reason can be assigned for separating necessitudo and necessitas. 3 Accordingly, in the books of the early writers you may often find necessitudo used of that which is necessary; 4 but necessitas certainly is seldom applied to the law and duty of respect and relationship, in spite of the fact that those who are united by that very law and duty of relationship and intimacy are called necessarii (kinsfolk). 5 However, in a speech of Gaius Caesar,7 In Support of the Plautian Law, I found necessitas used for necessitudo, that is for the bond of relationship. His words are as follows:8 "To me indeed it seems that, as our kinship (necessitas) demanded, I have failed neither in labour, in pains, nor in industry."