"of the nature of a paradox," 1580s, from paradox + -ical. Meaning "inconsistent with itself" is by 1630s. Competing forms were paradoxal (1560s), paradoxial (1620s), but these survive in niches, if at all. Related: Paradoxically.
it is paradoxical that standing is more tiring than walking
paradigm
paradise
paradisiacal
parados
paradox
paradoxical
paradoxology
paraesthesia
paraffin
paragon
paragraph