Affixoids may lead to affixes
The change of an affixoid into an affix can be observed by comparing the Dutch noun hoofd ‘head’ and its German prefix counterpart Haupt- ‘main’. In German, the word Haupt that is the historical equivalent of Dutch hoofd has been superseded by the word Kopf to denote the upper body part. In the text of Bach’s Matthew Passion (composed in 1727) we can still observe the use of Haupt as a free form in the choral Oh Haupt voll Blut und Wunden ‘O head full of blood and wounds’, but the productive use of Haupt as a free word is no longer possible in modern German, and has gradually disappeared. This is why in present-day grammars of German the morpheme Haupt- in words like Haupt-bahnhof ‘central station’ and Haupt-sache ‘main issue’ is qualified as a prefix. In other words, a prefixoid becomes a real prefix if the relevant word is no longer a free lexical item. The additional condition is that the prefixoid has a meaning that can be used productively. The loss of a word that is also listed as part of a complex word will not lead to an affix, but only lead to a cranberry morpheme (that is, a morpheme that only occurs as compound constituent) if that morpheme is not used for coining new words. This is the case for words like Dutch bruide-gom, German Brauti-gam and English bride-groom (all with the same meaning), where gom, gam and groom are cranberry morphemes. Hence, we do not consider the bound morphemes gom, gam or groom suffixes.
The rise of affixes from affixoids requires that language users conclude to abstract patterns that characterizes sets of compounds with the same bound meaning for one of their constituents, and thus supports the use of constructional idioms for the proper characterization of affixoids.