そんな態度は慣れっこだ
そんな難しいことはできっこない
From my exposure so far it seems っこ is along the lines of having been able to do something, and っこない is not being able to do something. What's the precise meaning?
Also, where does it come from - is it dialectical or regional? Is it a new usage uncommon in older speakers? Is it considered slang?
Etymologically, っこ can be considered as one of the Japanese suffixes that work as an diminutive, like -ie as in doggie. It can attach to some nouns and the masu-stem of certain verbs. It may or may not mean the same thing as the original word. It can have many unique meanings derived from the original word, especially when it's used with a verb.
- 端っこ ≒ 端
- すみっこ ≒ すみ
- 根っこ ≒ 根
- 慣れっこ ≠ 慣れ
- かけっこ ≠ かけ
- にらめっこ (from 睨む)
- とりかえっこ
Perhaps other common words like ごっこ and おしっこ are etymologically related to this. These words sound more or less cute or childlike. Basically you have to memorize each word with its meaning. It's not necessarily dialectal (the words listed above are not dialectal), but some dialects such as Tohoku-ben use it a lot. Words like 嫁っこ or 飴っこ sound dialectal to me.
It does not mean "able" by itself, but masu-stem of verb + っこ + ない is a colloquial pattern that means "cannot / no way".
- 泳げっこない。 No way I can swim.
- 見えっこないって。 No way we can see it.
- 受かりっこありませんよ。 There is no way you will pass (the exam).
There is another っこ (っ子), which is a suffix that means "child".
- ひとりっ子 an only child
- 博多っ子 children in Hakata (city)
- おばあちゃんっ子
- ぶりっこ
- テレビっ子
