Other Indo-European loans
Loans into Proto-Germanic from other Indo-European languages can be relatively dated by how well they conform to Germanic sound laws. Since the dates of borrowings and sound laws are not precisely known, using the loans for absolute, or calendar, chronology would be impossible.
Most loans from Celtic appear to have been made before or during the Germanic Sound Shift. For instance, one specimen *rīkz 'ruler' was borrowed from Celtic *rīgos 'king', with g → k. It is clearly not native because PIE *ē → ī is not typical of Germanic but is a feature of Celtic languages. Another is *walhaz "foreigner; Celt" from the Celtic tribal name Volcae with c → h and o → a. Other likely Celtic loans include *ambahtaz 'servant', *brunjōn 'mailshirt', *gīslaz 'hostage', *īsarna 'iron', *lēkijaz 'healer', *lauđan 'lead', *Rīnaz 'Rhine', and *tūnaz, tūnan 'fortified enclosure'. These loans would likely have been borrowed during the Celtic Hallstatt and early La Tène cultures when the Celts dominated central Europe, although the period spanned several centuries.
From East Iranian have come *hanapiz 'hemp' (cf. Persian kanab), *humalaz, humalōn 'hops' (cf. Ossete xumællæg), *keppōn ~ skēpan 'sheep' (cf. Pers čapiš 'yearling kid'), *kurtilaz 'tunic' (cf. Ossete kwəræt 'shirt'), *kutan 'cottage' (cf. Pers kad 'house'), *paidō 'cloak', *paþaz 'path' (cf. Avestan pantā, g. pathō), and *wurstwa 'work'. These words were surely transmitted by either the Scythians or later groups such as the Sarmatians from the Ukraine plain where Germanic peoples and Iranians had protracted interaction. Unsure is *marhaz 'horse', which was either borrowed directly from Scytho-Sarmatian or through Celtic mediation.
Non-Indo-European elements
The term substrate with reference to Proto-Germanic refers to lexical and phonological items that do not appear to be explained by Indo-European etymological principles. The substrate theory postulates that these elements came from a prior population that remained among the Indo-Europeans and was sufficiently influential to transmit some elements of its own language. The theory of a non-Indo-European substrate was first proposed by Sigmund Feist, who estimated that about 1/3 of the Proto-Germanic lexical items came from the substrate.
Transcription
The following conventions are used in this article for transcribing Proto-Germanic forms:
Voiced obstruents appear as b, d, g; this does not imply any particular analysis of the underlying phonemes as stops /b/, /d/, /ɡ/ or fricatives /β/, /ð/, /ɣ/. In other literature, they may be written as graphemes with a bar to produce ƀ, đ and ǥ.
Unvoiced fricatives appear as f, þ, h (perhaps /ɸ/, /θ/, /x/). /x/ may have become /h/ in certain positions at a later stage of Proto-Germanic itself. Similarly for /xʷ/, which later became /hʷ/ or /ʍ/ in some environments.
Labiovelars appear as kw, hw, gw; this does not imply any particular analysis as single sounds (e.g. /kʷ/, /xʷ/, /ɡʷ/) or clusters (e.g. /kw/, /xw/, /ɡw/).
The "yod" sound appears as j /j/. Note that the normal convention for representing this sound in Proto-Indo-European is y; the use of j does not imply any actual change in the pronunciation of the sound.
Long vowels are denoted with a macron over the letter, e.g. ō. When a distinction is necessary, /ɛː/ and /eː/ are transcribed as ē¹ and ē² respectively. ē¹ is sometimes transcribed as æ or ǣ instead, but this is not followed here.
Overlong vowels appear with circumflexes, e.g. ô. In other literature they are often denoted by a doubled macron.
Nasal vowels are written here with following N, e.g. ôN /õːː/. Most commonly in literature, they are denoted simply by a following n. However, this can cause confusion between a word-final nasal vowel and a word-final regular vowel followed by /n/; a distinction which was phonemic. Tildes (ã, ĩ, ũ...) are also used. Don Ringe denotes them with ogoneks (ą, į, ų...).
Diphthongs appear as ai, au, eu, iu, ōi, ōu and perhaps ēi, ēu.[25] However, when immediately followed by the corresponding semivowel, they appear as ajj, aww, eww, iww. This convention is based on the usage in Don Ringe's recent book From Proto-Indo-European to Proto-Germanic.