Fox is one animal name backed by a longish tradition, and then popularized via the lead character Fox Mulder on X Files. Fox is simple, sleek, and a little bit wild, and could make an interesting middle name.

Although Greek in origin--in the fourth century, a bishop by that name established the principles of the Greek Orthodox Church--Basil for years took on the aura of aquiline-nosed upper-class Britishness of Sherlock Holmes portrayer Basil Rathbone, then spiced with the fragrant aroma of the herb that entered with the Pesto generation.

Like many short forms now popular as full names in the Netherlands, Coen—also spelled Koen—originated as the diminutive of the more old-fashioned Coenraad, the Dutch Conrad. In this case, it would be pronounced as KOON, with a short oo sound.
Alternatively, it may be used in the US as a variation of Cohen, which stems from the Jewish surname designating a priest, and thus pronounced as CO-uhn. Additionally, it may also relate to the Irish surname McCown ("of Connacht") or to the Australian place name, Coen, meaning "thunder" from its Indigenous roots.

Theon, an ancient name attached to a noted Greek teacher of mathematics and astronomy, also father to the first woman mathematician, might appeal to parents in this field. You can think of Theon as Theo with something a little extra.

With a distinctive sound and a robust feel, Laith is a name that also has a touch of breezy charm to it. Currently in the UK Top 1000, it is a cross-cultural boy name that's also on the rise in the US.

This familiar but never popular Welsh surname name might be a good Sean alternative-- and we're starting to hear some berrybuzz about it. Vaughn is an alternate spelling.

Hearn is a masculine name of Anglo-Saxon and Irish origin functioning both as a surname and given name. It derives either from the Old English 'hyrne' meaning 'corner of land' or 'nook,' or from the Irish 'Ó hEachtighearna' meaning 'descendant of the horse lord.' Historically more common as a family name, Hearn appeared occasionally as a first name in medieval England and Ireland, often representing family connections. The name carries associations with nature through its possible connection to herons (though this is a folk etymology). With its strong single-syllable sound and heritage connections, Hearn appeals to parents seeking uncommon masculine names with historical depth. Though rare in contemporary use, it shares qualities with popular short surnames-turned-firstnames like Hayes and Reid.