Anglo-Saxon.English.
Innema (inn-ema),Inmost (in-m-ost).
Ûtema (ût-ma),Outmost (out-m-ost).
Siðema (sið-ema),Latest.
Lætema (læt-ema),Latest.
Niðema (nið-ema),Nethermost (neth-er-m-ost).
Forma (for-ma),Foremost (fore-m-ost).
Æftema (aft-ema),Aftermost (aft-er-m-ost).
Ufema (uf-ema),Upmost (up-m-ost).
Hindema (hind-ema),Hindmost (hind-m-ost).
Midema (mid-ema),Midmost (mid-m-ost).

Now the words in question show at once, that, as far as they are concerned, the m that appears in the last syllable of each has nothing to do with the word most.

From the words in question there was formed, in Anglo-Saxon, a regular superlative form in the usual manner; viz., by the addition of -st; as æfte-m-est, fyr-m-est, læte-m-est, sið-m-est, yfe-m-est, ute-m-est, inne-m-est.

Hence, in the present English, the different parts of the syllable most (in words like upmost) come from different quarters. The m is the m in the Anglo-Saxon words innema, &c.; whilst the -st is the common sign of the superlative. Hence, in separating such words as midmost into its component parts, we should write

Mid-m-ostnotmid-most.
Ut-m-ostut-most.
Up-m-ostup-most.
Fore-m-ostfore-most.
In-m-ostin-most.
Hind-m-osthind-most.
Out-m-ostout-most.

[§ 260]. In certain words, however, the syllable m-ost is added to a word already ending in -er; that is, already marked with the sign of the comparative degree.

Neth-er-m-ost.Hind-er-m-ost.
Utt-er-m-ost.Out-er-m-ost.
Upp-er-m-ost.Inn-er-m-ost.