Re-reading the intriguing book by Merritt Ruhlen: On the Origin of Languages: Studies in Linguistic Taxonomy. The basic premise is that contrary to widespread belief, the tools of comparative linguistics can be applied beyond the Indo-European family to reconstruct the roots of a world proto-language. Though it sounds far-fetched at first, Ruhlen makes a compelling case for his methodolgy, and gives some world-etymologies that I can't resist from reproducing below. It gives me particular satisfaction to see these ancient roots manifest themselves in the languages I read, write and speak: Russian, English, Hebrew, Latin. The asterisk indicates an unattested form.
KAMA 'hold (in the hand)'. Ruhlen gives the Proto-Afro-Asiatic root *km, from which we get the Arabic kamasa 'seize, grasp'. Could the Hebrew חמש 'five' be related (as in, the five fingers of the hand)? The Indo-European cognate is *gemo, which appears in Russian as жму 'I press'.
My favorite: MANA 'to stay (in a place)'. Proto-Afro-Asiatic: *mn, which manifests in Hebrew as אמן. This root means 'true, enduring', and is borrowed by many Indo-European languages as amen. Of course, the I-E family has this root occurring natively as well -- as the Proto-IE *men. The Latin manere will be more familiar to English speakers as remain.
Another favorite: MENA 'to think (about)'. Hebrew: מנה 'to count'; English: mind, mental; Russian: мнить.
I'll close with the colorful PUTI 'vulva'. Hebrew speakers will immediately recognize this as פות, via the Proto-Afro-Asiatic *pwt 'hole, anus, vulva'. Speakers of Romance languages might be pleased to learn that when they curse a woman as puta(-na), they're invoking an ancient root, dating back tens of thousands of years!
A final note, and an appeal to my more professional linguist readers. Ruhlen writes: "the Indo-European family has been established beyond doubt," and this has been my belief ever since I began to amateurishly dabble in comparative linguistics. However, I recently had an argument with a computational linguist/computer scientist/mathematician who claims that the IE-family is "merely" a hypothesis, and a rather controversial one at that. Does anyone know of a reputable linguist who doubts the common origin of the so-called Indo-European languages, and questions the basic structure of reconstructed Proto-IE?
Update: More world etymologies are available online.
Update II: To be fair and balanced, I'm linking to a harsh critique of Ruhlen and his methods, with a hat tip to Cosma.