أو أخذ بعض اللفظ لا كله
Or taking part of the wording rather than the whole of it.
Here some recognizable vocabulary or phrasing survives, while the later poet supplies other words. This differs from mere agreement in a broad poetic theme, since a particular verbal connection can be examined.
One shared ordinary word does not, by itself, establish such a case. The relevant question is whether the taken portion represents a distinctive earlier expression and how the resulting composition compares with its predecessor.