The earlier declensional classes of Old Frisian had gradually been worn down towards the close of the Middle Ages, leaving only incidental lexical vestiges. One of these vestiges is a set of 15 nouns, which still show archaic, but synchronically irregular, plural forms in the early 17th century. We traced their development throughout the following centuries. Only eight of them preserve their 17th century plural form in the written language until the 20th century and even fewer are intact in present-day spoken Frisian. Statistical analyses were performed to find out which factors correlate with retention. It turns out that the absolute and proportional frequencies of the plural form, as well as the salience of the ending, contribute in almost equal proportions to the retention of the plural form. The diachronic regularisation of the studied lexical items can to a large extent be predicted from these 3 variables.

中文翻译：

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促进违规行为保留的因素

中世纪弗里斯兰语的早期变形等级逐渐被淘汰，直到中世纪末期，仅留下了偶然的词汇遗迹。这些痕迹中的一个是一组15个名词，在17世纪初期，它们仍然显示出古老但同步不规则的复数形式。我们追踪了其后几个世纪的发展。直到20世纪，它们中只有八种以书面语言保留其17世纪的复数形式，而如今的弗里斯兰语则保持不变。进行统计分析以找出哪些因素与保留率相关。事实证明，复数形式的绝对频率和比例频率以及结尾的显着性对保持复数形式几乎成比例。