Although Part-of-Speech (POS) tagging has been widely studied, it still presents several challenges, particularly reduced performance on out-of-domain data. While increasing in-domain training data can be effective, this strategy is often impractical in historical low-resource settings. Cross-lingual transfer learning has shown promise for low-resource languages; however, its impact on domain generalization has received limited attention and may remain insufficient when used in isolation. This study focuses on cross-lingual and cross-domain transfer learning for POS tagging on four historical Germanic low-resource languages in two literary genres. For each language, POS tagged data were extracted and mapped to the Universal Dependencies UPOS tag set to establish a monolingual baseline and train three multilingual models in two dataset configurations. The results were consistent with previous findings, indicating that structural differences between the genres can negatively influence transfer learning. The poetry-only multilingual model showed improvements within that domain compared to the baseline. In contrast, multilingual models trained with all available data had lower performance caused by substantial structural differences in the corpora. This study underlines the importance of investigating the domain-generalization abilities of the models, which may be negatively influenced by substantial structural differences between data. In addition, it sheds light on the study of historical low-resource languages.

Poetry has always distinguished itself from other literary genres in many ways, including grammatically and syntactically. These differences are evident not only in modern literature but also in earlier stages. Linguistic analysis tools struggle to address these differences. This paper focuses on the dichotomy between Old English poetry and prose, specifically in the context of the POS tagging task.Two annotated corpora representing each genre were analyzed to show that there are several types of structural differences between Old English poetry and prose. For POS tagging, we conduct experiments on both a detailed tag set with over 200 tags and a mapping to the UPOS tag set with 17 tags. We establish a baseline and conduct two cross-genre experiments to investigate the effect of different proportions of prose and poetry data. Across both tag sets, our results indicate that if the divergence between two genres is substantial, simply increasing the quantity of training data from the support genre does not necessarily improve prediction accuracy. However, incorporating even a small amount of target data can lead to better performance compared to excluding it entirely. This study not only highlights the linguistic differences between Old English poetry and prose but also emphasizes the importance of developing effective NLP tools for underrepresented historical languages across all genres.