The word holn is a colloquial contraction of holen.
Just the way to omit the e in the written word is unusual, but in spoken language, this is a normal variation of pronunciation of many words. This has to do with how to pronounce ...
When talking about stressing of syllables, German has three types of syllables:
- betonte Silben (stressed syllables)
- unbetonte Silben (unstressed syllables)
- Reduktionssilben (reduction syllables)
Reduction syllables can be seen as a subset of unstressed syllables, i.e they are even less stressed than normal unstressed syllables, and they are characterized by there properties:
- Only the last syllable of a word can be a Reduktionssilbe.
- When written, a Reduktionssilbe always contains the letter e.
When spoken, the vowel of a Reduktionssilbe is either:
- [ə] (mid central vowel, aka schwa) like in Torte, dieses, Rahmen ([ˈtɔʁtə], [ˈdiːzəs], [ˈʀaːmən])
- [ɐ] (near-open central vowel) like in Bauer, Federn, hundert ([ˈbaʊ̯ɐ], [ˈfeːdɐn], [ˈhʊndɐt])
- missing, i.e. a sonor consonant (often n or l) is the core of the syllable like in Leben, Regel, jodeln ([ˈleːbn̩], [ˈʀeːɡl̩], [ˈjoːdl̩n])
German vocabulary is full of words, where the last syllable is slowly shifting from type 1 to type 3 within a longer period of time, or exists in both forms. Most of them are words ending in -en like:
- Regen [ˈʀeːɡən], [ˈʀeːɡn̩]
- sollen [ˈzɔlən], [ˈzɔl̩n]
- laufen [ˈlaʊ̯fən], [ˈlaʊ̯fn̩]
And of course also
- holen [ˈhoːlən], [ˈhoːl̩n]
Sometimes an author explicitly wants to mark, that such a word should be pronounced without a vowel in the last syllable (for example in poems where pronunciation can be important for rhythm and rhymes). The standard way to do this is to use an apostrophe (soll’n, hol’n), But some authors prefer not to this, and then you get Regn, solln, laufn, holn. But non of these spellings is standard German spelling. When a student writes this, his teacher would mark it as an error.