Wondrous means filling you with wonder. A wondrous sight, wondrous strange, wondrous things.
It is deliberately archaic or poetic — nobody says it plainly — and it belongs to hymns, fantasy and Shakespeare. Wondrous strange is from Hamlet. As an adverb it once meant wonderfully, which is why wondrous strange is grammatical rather than a slip. Note wonderful, which took over the ordinary work; and that wondrous was formed by mistake, from an old genitive that looked like an -ous ending.
1adjectivewondrousFilling you with wonder.
“The children stared at the wondrous lights of the fair as it came to life.”
synonyms: marvellous, wonderful
wondrous is a quality of wonder.
Middle English wonders was a genitive form meaning of wonder, and it was reshaped to wondrous because it looked as though it should end in -ous. The word is a spelling error that stuck.
Middle English
wondrous
English, today
wondrous
Built from
From Middle English wondrous, alteration after the suffix -ous of Middle English wonders (“wondrous, wonderful”), from Old English wundres (“of wonder”), genitive singular of wundor (“wonder, miracle”), from Proto-Germanic wundrą (“wonder”). Compare Dutch wonder, German Wunder.
Etymology from Wiktionary, CC BY-SA