The Pieta is the most detailed and finished of his important carvings, a work that repays the closest inspection.

《 圣母怜子像》是他那些重要作品中最精细最完美的一件，值得全心投入地去细致观察。

youdao

So, Pynchon is using that religious vocabulary: not just the religious imagery of the Pieta, but the religious vocabulary of the capitalized Word.

这个宗教的词语：,不仅仅是圣像雕塑，还有这个大写的“Word“

耶鲁公开课 - 1945年后的美国小说课程节选

And the image is much more specifically of Michelangelo's Pieta.

这一幕像极了米开朗基罗的圣母哀子像。

耶鲁公开课 - 1945年后的美国小说课程节选